Electrical contact element and process of making same



Dec. 8, 1931.

M. C. BURR ELECTRICAL CONTACT ELEMENT AND PROCESS OF MAKING SAME Filed May 6, 1929 l N VEN TOR.

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ATTORNEYS,-

Patented Da e, 1931 UNITED STATES PATENT OFFICE C. BURB, OI CINCINNATI, OHIO, ASSIGNOR '1'0 BOXILL-BBUEL CARBON M- PANY, OF OINGINNATI, OHIO, A CORPORATIOQN' OF OHIO ELECTRICAL CONTACT ELEIENT AND PBOOESB 0F. mme SAME Application filed m a,

1829. a Serial No. 361,005.

The mixture of desired percentages of the various ingredients have been pressed in a mold and then baked. In order to provide a suitable contact portion for the attachment ofan electric wire to the brush, it has further been suggested that the surrounding surfaces about the orifice through which the contactlug'is to be attached be plated or coated with copper. A connection thus made will point of contact.

' The plating of the brushes as above suggested hasbeen expensive and has not result ,ed in obta ning the best results, and it is the object of niy invention to provide a process which will in some instances make the platmg of the portion of the brush to which the wire is to be attached unnecessary, and in other instances make a portion which may be much more readily coated or plated if this operationis stillthought to be necessary.

It is specifically my object to make a brush which will have the portion thereof to be exposed to the commutator of substantially the same ingredients as have formerly been used, and to antegrally mold and'bake with this composition, a portion to which the wire will be attached which will have as part of its composition a substantial amount of a pow dered metal such as copper or aluminum, WhlCll will thus greatly increase its conducltivity and cut. down losses due to resistance d heating up at the juncture of the wire and the brush.

( with twenty five. percent wide range of proportions and ingredients which may be used in the making of the brush. As a specific exam le of one method, I take fifty percent of powdbred petroleum coke, ten percent of natural graphite and forty percent of coal tar pitch. These ingredients I mix in a heated mixer, heated sufliciently so that the pitch will melt. The entire mass is thoroughly worked up and then allowed to oool--and agglomerate in lumps. It is then pulverized. I then take a 'batch of fifty percent of finely powdered copper and mix it o graphite and twenty five percent ofcoal tar pitch and mix avoid resistance losses and heating up at the I above suggested, which is so formed'that' v In carrying out my invention there is a.

. therewill be no line of weakness ture of the materials com at the juncgredients and It 1s further my ob ect to make a brush as the ingredients independently in another heated mixer. This mixture is then allowed to cool and it is then'finely ground up.

Into a mold having a cavity shaped according to the brush which is my desire to make, I deposit in one ortion the first mixture above noted conslsting of the carbon and pitch, and into another portion of the cavity I deposit the second named mixture containing the metalpowder. I may provide a wall in the mold subdividing the two mixtures. I then remove the subdividing wall and appl pressure to the mold. Ordinaril the mo ding will be accomplished in a hy raulic press. After removal fromthe press I bake the'molded product and the mtegral formation above noted is formed, which does not have a weakened cleavage line at the juncture .line of the two different in edients. V

' t should be understood that the inventive principleinvolved consists, in its broader asects, in the provision of an integrally ormed brush piece having variable resistance in the component parts. While I have, in the example cited above, specified particular ingredients there is a wide scope of inrcentages with which the invention may b: practiced. In the example cited the portion of the brush containing the metalpowder will have a ton hened surface which ordinarily will avoi the necessity of metal supporting plates or holders.

or example, 1n the manufacture of the armature en gin endof the brush I may use lampblac artificial graphite and various bituminous tars and pitches or other carbonaceous binders; The percentages may also be varied. I

In the contact (and of the brush- I may use from fifteen to eighty percent of powdered'copper or aluminum or other suitable powdered metallic conductors. Further, the percentages of carbon composition and bituminous or carbonaceous binders may also be varied to meet particular conditions.

In the drawings:

Figure 1 is a perspective view of one type of commutator brush.

Figure 2 is a section along the lines 2-2 in Figure 1.

The brush has the commutator contacting portion 1 composed of the powdered coke,

- graphite and coal tar pitch. The conductor contacting end 2 is composed of finely divided copper, graphite and coal tar pitch. The block is integrally molded in a mold which forms a groove 3 at the contacting end for the reception of a contact wire 4 which is soldered withinthe recess in the brush.

Other sizes, shapes and forms of brushes may, of course, be molded to suit the particular requirements of the use to which they are to be'put.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

1. A commutator brush having one end composed of carbon and a carbonaceous binder, and the other composed of carbon, a carbonaceous binder andmetal powder.

2. An integrally molded commutator brush having a commutator contacting end of relatively high resistance and having a carbonaceous composition, and a conductor contacting end having a relatively low resistance andhaving in' its composition a por-i tion of finely divided metal.

3. An integrally molded commutator brush having a commutator contacting end formed ofcarbon and a carbonaceous binder and a conductor contacting end of relatively lower resistance having a composition comprising carbon, a carbonaceous binder and finely divided copper.

4. An integrally molded commutator" brush having the commutator contactingportion thereof of relatively high resistance, and havingv a carbonaceouscomposition, and a conductor contacting portion having a relatively low resistance and having in its composition a portion of finely divided metal.

MYRTIGE o. BURR. 

